This invention refers to the binding of electric conductors, and the like, placed together in a bundle; in particular, it applies to a method and to an automatic apparatus capable of positioning a portion of a plastic strap supplied in the form of a continuous band that is automatically fed by passage through a plastic head or hollow retaining element supplied as a continuous strip until it wraps the bundle of cables with a portion of the band, the ends of which are clamped by a retaining element; a compact binding is thus obtained that is stretched to the desired value. Previous automatic devices for binding cables made use of a loading mechanism containing a number of separate shaped bands of fixed length which were fed in succession to a distributing device that was part of the apparatus.
The use of a loader for feeding bands to an automatic device to achieve the binding of cables, gives rise to working difficulties which impair the efficiency of the apparatus. Any type of apparatus which makes use of a loader is limited to the application of as many bands per cable as can be held by the loader that, when empty, must be replaced with a full one every time the previous one becomes exhausted, or it must be reloaded with new straps properly oriented and compatible with the particular type of distributor of the apparatus.
Practical limitations due to the size of the bands and to the necessity of using a portable device, easy to handle where space is at a premium, have restricted to 100 the number of bands for each loader.
Other previous automatic devices for binding cables made use of preformed straps with a preset length, held in a parallel position by means of a supporting strip wound as a coil with a large number of strps. The straps are fed by a secondary and separate device connected to a tube for feeding the portable apparatus for binding cables.
The secondary device was used for supporting the coil of straps, for separating one of them from the supporting strip at every cycle and for feeding it, through a channel, to the portable apparatus.
Still other devices for binding cables with preformed fixed-length straps, made use of a very large loading device placed on a secondary apparatus that, for each cycle, had to feed the portable applicator through a connecting tube.
All previous devices, whether using a loader or a secondary feeding mechanism, hence at an additional cost, make use of preformed straps of preset length consisting of a flexible portion (tongue) and one for clamping (head).
The strap, fed from a loading device or from a secondary apparatus, was made to advance inside the portable applicator by means of mechanical devices that were very complex, had to be very precise and, hence, were very expensive to manufacture.
The straps, thus fed by means of the portable applicator, wrapped the bundle of cables positioned across the axis of the device, while running through a guiding channel; the end of the flexible portion of the strap (tongue) would pass through the clamping section (head) to be engaged by an internal device within the applicator which stretched the tongue until the bundles of cables had been clamped within the desired value.
Once the clamping had been achieved, an additional device inside the portable applicator would cut the excess portion of the tongue; this had to be expelled in such a way as to avoid the blockage of the guiding channel which would have, otherwise, prevented the correct positioning of the strap to be used next.
Such a system required interacting movements and mechanical elements driven by very complex pneumatic or electro-pneumatic actuators which were the cause of frequent obstructions and subsequent loss of efficiency. For those reasons, previous cable binding devices required the use of straps of preset length, fit to cover a range between minimum and maximum diameters; this arrangement led, invariably, to the waste of a portion of the tongue, the length of which was a function of the diameters of the bundles of cables.
This excess portion of the tongue, not only constituted a waste and, hence, an additional cost, but could also jam the apparatus and become a nuisance to the surrounding electrical equipment, because of the excess materials produced falling from the straps.
To avoid this inconvenience, some previous devices made use of special containers connected to the portable applicator which, however, due to the difficulties of maneuvering this type of machinery in small spaces, presented the problem that the rejected portion of the tongue might be caused to bounce and to return inside the apparatus. This occurrence would lead to the jamming of the apparatus, particularly when it had been rotated through 90.degree. or more for the binding of vertical bundles. Another difficulty with previous devices is due to the fact that the use of pneumatic equipment interacting with various mechanical elements, makes the equipment extremely delicate; the correct operation of the equipment, in fact, depends on the quality of the pneumatic control and driving components, which are usually highly delicate, so any small pressure variation may upset the synchronism of the various movements. This may jam the mechanism and break some of the internal mechanical components, thus necessitating expensive maintenance and loss of efficiency.
An object of this invention, therefore, is to provide an automatic cable-binding apparatus which makes use of a special binding device that includes a correctly dimensioned and specially profiled plastic strap that automatically couples with a retaining element, also made of plastic material and constructed in such a way that the two joined elements, for each working cycle, adjust to the size of the bundle and bind it to the desired degree of tightness.
Another object of the invention is to provide an automatic cable-binding device capable of a large number of successive bindings by automatically feeding the binding elements supplied in the form of a continuous band, for the plastic strap, and of a strip, for the retaining element.
Another object of this invention is to provide an automatic cable-binding apparatus with a mechanism controlled by an electric motor and, hence, without pneumatic driving devices; this eliminates all problems connected with the availability of compressed-air lines, and with the safety of the operation in as much as the apparatus makes no use of fast-acting mechanical elements for power transmission that may cause injury to the operator.
Another object of the present invention is to provide an automatic apparatus for binding cables which utilizes the exact quantity of plastic strap according to the diameter of the bundle to be bound. This avoids waste of material, does not require the expulsion of scrap and does not create pollution problems.
Another object of the present invention is to provide an automatic cable binding apparatus of reduced dimensions, light and handy, for the binding of cables where space is limited, as it would inside electrical equipment.
Yet another object of this invention is to provide an automatic cable binding apparatus driven by a low-voltage electric motor, that interacts with simple and sturdy mechanical elements and is easy to maintain so as to reduce manufacturing and operating costs.
The automatic apparatus for binding cables according to the method of this invention, includes a mechanism made of a series of interacting linkages and a motor-driven mechanism which, working together during every cycle, allow for: the advance of a strip made of many toothed retaining elements, the separation of one of them and its alignment for matching with a toothed or serrated binding strap which is made to advance automatically by the electric motor, by inserting the end of the strap through the retaining element, in the pushing direction, until the end of the strip, as it runs inside a guide, wraps the bundle of cables and is reinserted through the opposite side engaging the inside of the toothed retaining element; the stretching of the strip until the cables are tightened within the set value; and the cutting of the strip to perform a binding for every working cycle.
The plastic strap, used with the automatic apparatus for the binding of cables, is in the form of a continuous rectangular-shaped hand having, on one of its major sides, a series of indentations, along two parallel lines, with opposing teeth.
The retaining plastic element used in the automatic binding apparatus, is made of a molded strip composed of several elements joined together by an intermediate portion.
The retaining element has an approximately square shape, it is hollow along the axis and is provided, internally, with two flexible and opposing arms with a set of teeth properly sized to match the indentations of the plastic strap.
The matching of the retaining teeth on the indentations of the strap, that are under the pulling action, causes the retention of the two ends of the strap that are engaged inside the retaining element.